Acid Rain in our Natural Environment

This topic submitted by Megan Smith, Ariel Flowers, David Marimon, Alex White, Joe Riffe (megjs_5@hotmail.com) at 5:53 PM on 12/5/02.
Additions were last made on Wednesday, May 7, 2014. Section: Negron-Ortiz

Introduction: We are interested in studying the effects of acid rain on winter rye, blue bush beans and radishes in both seedlings and 3-week old sprouts. While brainstorming for ideas, we visited the greenhouse and decided to do a project involving plants. After much thought, we decided on a test that would demonstrate effects of acid rain occurrences in nature. Hence the idea of the acid rain test. We are mimicking the effects of acid rain in our experiment and comparing it to the effects of acid rain in our natural environment. In order to test the effects on these plants, we are watering the plants with HCl for different pH concentrations. We hypothesize that our control group, the plants being watered with tap water (pH 7) will be the only specimens to survive. In this experiment we plan to learn: 1) about the effects of acid rain on plants in general 2) how different levels of pH will affect different species 3) what is the lowest pH concentration a plant can tolerate. Inversely, we will learn the long term affects that acid rain has on our environment and how that can endanger some plant species. We also want to determine which plants are more adaptable to changes in the environment, and at which stages in their life cycle they are more adaptable using seedlings and sprouts. Using information from the EPA, we decided to test our control group at a pH concentration of 7.0, which is tap water. Other testing degrees will be pH concentrations 1.0, 3.0 and 5.0, each degree away from 7.0 being ten times as acidic. Research done by the EPA also provided us with a way to measure height as a factor in monitoring the effects of acid rain on plants. Since acid rain is likely to only weaken trees by damaging their leaves, delaying their growth, rather then killing them directly, we have decided to measure plant height, in centimeters, testing the idea that high acidity will delay growth. (U.S. Environmental Protection Agency 2002). A group of scholars, testing the effects of acid simulation on Norway Spruce buds, gave us the idea to test seedlings as well as plants. When buds were tested with pH concentrations as low as 2.9 and 3.9 for a period of two years, they ultimately died. (Albrechtova, J., et al, 2002). We also decided to test our plants wih concentrations of 1.0 and 3.0, while using hardy plants, after researching the work of another group of scholars. They tested insensitive plant, the Oshima cherry. Simulating acid rain, with pH concentrations ranging from 1.0 to 4.0, droplets were placed on the leaf surface, lowering the pH concentration, only slightly. (Kohno, Y., et al, 2001).Other research led us to the use of hydrochloric acid as a basis for the different pH concentrations. A group studying for four years tested components of polluted rain using nitric acid, sulfuric acid, and ammonium sulfate. However, due to limited availability and financial constraints, we could not use all of these chemicals when testing so our group settled for HCL. (Bolger, T., Heneghan, L., 1996) Another study gave us the idea of pouring our acidic concentrations directly into the soil. This group, when testing with a pH concentration of 5.7, showed that there was much change in the nutrient content of the soil and that the organic matter had actually decreased. (Cho, JY., et al, 2002).

Materials and Methods: We are investigating two different groups. Our first group is of 6-week old plants composed: 8 pots of winter rye plants, 8 radish plants, and 8 blue bush bean plants, each pot containing one plant. Our second group: 1-week old seedlings composed of 8 pots of winter rye plants, 8 radish plants and 8 blue bush bean plants, each pot containing one plant. Two pots of each species, making 8 groups of 6 total, and each group will be watered with a pH concentration of 1.0, one with a pH concentration of 3.0, another with a pH concentration of 5.0, and the last with tap water. pH levels will be regulated with HCL. Our project is statistically sound because we have a control group of 12 plants, sprouts and seedlings, and a logical hypothesis, which should be easy to test using the methods of the t-test. Also, we are using a large sample of plants so as not to have a biased outcome. In order to prevent our test from being biased, we will measure an equal amounts (30 ml) of water/HCL to water the plants with three times a week. We will keep consistent with our watering and measuring height. We will have the class help us with our experiment by doing various things. They will make visual observations recording findings such as plant height, color change, wilting, and any decay. After their observations, we will have the class water the plants with the varying acidic water. The class will not process data. We will do that later as a group at the end of our experiment. Data that we will be recorded on a regular basis, including the height of the plants. Our research will show whether this factor is closely correlated to the degree of pH concentration. Important materials that we are using include the plants we are testing: 6-week old winter rye plant, radishes and blue bush beans. Winter rye seeds, blue bush bean seeds, and radish seeds, HCL to control pH levels, water, soil and 24 pots. We will keep our plants in the greenhouse connected to Boyd Hall, and consistently water them three times a week, making observations each visit. Timeline:Tuesday 10/1: Plant first grouping of plants (8 winter rye, 8 radish, 8 bean) and water— greenhouse staff will water for the rest of the month.Tuesday 10/29: plant seedlings and water—greenhouse staff will water for the rest of the weekThursday 10/31: take pictures, prepare materialsTuesday 11/5: water, measure and take picturesThursday 11/7: water, measure and take picturesSunday 11/10: water, measure and take picturesTuesday 11/12: water, measure and take picturesThursday 11/14: water, measure and take picturesSunday 11/17: water, measure and take picturesTuesday 11/19: water, measure and take picturesThursday 11/21: discuss and collect results

Results: Included with data section

Questions: Once the experiment was completed, we felt we had a better grasp on the concepts behind our acid rain simulation. To answer the questions we asked ourselves at the beginning of the experiment, we consulted our results and came up with some striking conclusions. When reviewing the results of our now, nine-week old plants as compared to our now 4-week old sprouts, results show the nine-week old plants had a better tolerance of the varying pH concentrations. Little change, if any at all was observed in the all of the plants: radishes, winter rye, and beans. The seedlings however reacted very differently to the significant changes in pH concentration. All except one of the radish seedlings being watered with the concentration of 1.0 and 3.0 died after the sixth measurement was taken, the only surviving plant beginning to taper off. The radishes being watered with concentration of 5.0 and 7.0 were actually still growing! All of the bean seedlings watered with concentrations of 1.0 and 3.0 were already tapering off after the seventh measurement. From previous research, we can conclude that this tapering off is a sign that the plants will die soon. Like the radishes, those bean seedlings watered with concentrations of 5.0 and 7.0 were still in the growth process. Our winter rye plants proved to be the most remarkable, their seedlings remained unaffected to the varying changes in pH concentration. All winter rye seedlings continued to remain healthy. The nine-week old plants were for the most part unaffected by the varying levels in pH concentration. All radish and winter rye plants, regardless of pH concentration, measured in around the same height and remained consistent with growth patterns. The bean plants seemed negatively affected by the lower concentrations, because one of each watered with 1.0, 3.0 and 5.0 concentration died. We can conclude that the 5.0 plant died because it dried out, perhaps it missed a watering because the soil seemed much drier than the others, yet our 1.0 and 3.0 plants that lived seemed to be tapering off, suggesting that they were about to die. Besides our winter rye seedlings, all of other seedlings did not have the ability to adjust to acidic concentrations lower then 5.0. The plants proved much more adaptable to changes in acidity.Another factor tested was the lowest pH concentration a plant can handle. Obviously, all of the plants could handle the very acidic concentration of 1.0, yet some could not sustain life as long as others. Besides the winter rye seedlings, all other seedlings died off partway through the experiment, proving they could not live with pH concentrations as low as 1.0 and 3.0. If given more time, we assume that all of our nine-week old plants would probably survive at least another week. The basis of this experiment was to learn the effects of acid rain on the natural environment. After our experiment, we wanted to learn more about the long-term effects of acid rain. According to the Penn State University web site, the toxins in acid rain leach onto minerals in the soil, making it difficult for the plant to get the needed nutrients. Acid rain also “frees the toxic substances while dissolving the good ones through a complex combination of chemical reactions. As a result, the plants, already hindered in absorbing nutrients, experience a paucity of important nutrients that have been leached out of soil such as potassium, calcium, magnesium and sodium” (“Chemical”). Thus proves our assumption that the 9 week old plants watered with low, pH of 1.0-3.0, are likely to die off soon.

Discussion: This experiment proves that we must reject our former hypothesis that our control group, the plants and seedlings being watered with tap water (pH 7) will be the only specimens to survive. Although they deemed quite healthy, those plants and seedlings watered with a concentration of pH of 5.0 also proved to be just as capable of survival.

Seedling Results:As mentioned earlier, the seedlings being watered with pH concentrations of 1.0 and 3.0, experienced either death or were close to dying. But why did this happen? All of our high concentration (1.0 and 3.0) radish seedlings died, while those watered with a pH of 5.0 and 7.0 were still growing. By observing the root systems and consulting our resources, we have concluded that those radish root systems of high concentration were underdeveloped, causing the acid to leach to the minerals in the soil, before the radishes could absorb them. The roots appeared small and shriveled compared to a larger, lower concentration radish. There was a large difference in the acidity tolerance of the bean seedlings. While the 1.0 and 3.0 pH beans were near dead, the pH concentrations of 5.0 and 7.0 for the beans were continuing to grow at a steady rate. Towards the end of the experiment, the leaves of the1.0 and 3.0 bean plants were wilting and yellowing. The beans, being a more complex plant, probably had difficulty with photosynthesis. Acid rain tends to weaken a plant’s defenses, eating away at the waxy layer on the leaves, making them vulnerable (“Chemical”). The winter rye seedlings appeared to be unaffected by changes in pH concentration! Winter rye, being a grassy plant, is more than likely a hardy plant. Grass in general is able to sustain fluctuating levels of temperature, water, and pH concentration, as it is everywhere around us.

Plant Results:All of our plants seemed to do quite well with the changes in pH concentration however one of each of the 1.0, 3.0 and 5.0 beans did not survive, dying off probably due to the problem with photosynthesis. All of the radish and winter rye plants did quite well. They were most likely able to survive because they were given 6 weeks time to grow healthy root systems, before being affected with varying pH concentrations. One source mentions the idea providing that small amounts of acid in soil are good. When moisture lacks some acidity, the soil water has little ability to dissolve minerals and release their nutrients. Even though nutrients are present in the soil, the plants may not have access to them. It is said that “a strongly acidic soil is also detrimental to plant growth. In a soil that is too acidic, the soil moisture dissolves nutrients, which become leached away before they can be obtained by plant roots.” (Gabler, Petersen, Sager, Wise 1999) T-test Findings: A calculation of the P-values for all of the plant data proved to further support our findings. Since the P-values for each plant data were so small, ranging from .0001 to .0356, all less then the standard .05 value, there proved a significant difference among the growth rates of each plant and pH concentration. According to the bar charts, many of the plants appear to have remained consistent and alike, regardless of pH concentration! However, these results clearly show death rates, for example, with the adult bean plants. The histograms we constructed show in greater detail the growth rates and death rates of our plants.

Sources of Error: There are several sources for error within our experiment. One source, could be error on our part by not giving each plant exact amounts of water. One plant may have received slightly more water than another, giving it more a larger dose of the pH. Another source of error, since our plants were in the greenhouse and without a "no water" sign for a few days after we started watering with the different pH levels, there is a chance that they were still watered by the greenhouse staff with the fertilized water. This would give the plants a chance to receive more nutrients than we were planning and also give them the chance to be healthier than expected. A third source of error is that when it rained hard outside, the greenhouse would leak and water would drop from the ceiling. We had personal experience with drops hitting us while downstairs watering, so the likely-hood of the water landing on the plants is very high as well. They would be then receiving more water than we had planned on initially. A fourth source of error, although not our fault, would be the healthiness of the seeds and how likely they were to grow in the first place. It would depend on the plant as to whether or not it was ever going to have to the chance to grow to be healthy, etc.

Questions and Suggestions: As a group, we spent quite a bit of time researching and studying our methods and results that we have answered many questions on our own. However, we are still a little unclear on why our 9-week old plants seemed almost unaffected by the varying pH concentrations. Understanding that they are already established, we can conclude that they will eventually die off due to a lack of nutrients, however, why not die off sooner? What exactly does the acid do to the chemical composition of a plant? As a suggestion for future experiments, would be to research the chemical aspects of acid rain, rather then physical. To obtain more concise results, there are a number of things we could have done differently in this experiment. First off, we could have spent more time with our plants, taking measurements over a longer period of time. Second, we could have taken measurements everyday. Although this would be near impossible, due to our varying schedules, we might have gotten more concise results. Lastly, if space would allow, we could have planted our seedlings and plants in larger pots allowing their root systems to further expand, simulating more of a natural environment for them.

Bibliography: Acid rain is more likely to weaken trees by damaging their leaves rather than killing them directly. By damaging their leaves, the trees cannot receive as many nutrients, thus delaying their growth, or making them more susceptible to toxic substances. Trees high in the mountains are more likely to be damaged because of the higher amounts of acid clouds and fog. (U.S. Environmental Protection Agency 2002) Norway Spruce buds were tested at four years of age and subjected to acid rain simulation. pH concentrations of 2.9 and 3.9 were sprayed on the shoot systems for a period of two years. Conclusions prove a decrease in leaf primordial and a flatness of the apical meristem. These changes in the buds did not occur at all in the control group, providing that it was the effect of the acid rain that caused the destruction of the buds. (Albrechtova J., Opatina J., Soukupova J., Svobodova H., 2002) One group of scholars tested the effects of acid droplets of Sulfuric acid, with a pH ranging from 1.0 to 4.0 on the leaf surfaces of a sensitive plant, the Yoshino cherry, and a more insensitive plant, the Oshima cherry. The spot where the droplet was placed disappeared in both plants after 6 hours. The acidic water spread over the surface area, lowering the pH of the entire leaf only slightly. The group concluded that the leaves could neutralize the surface acid, possibly by ion exchange, in a relatively short amount of time. (Kohno Y., Matsuki R., Nomera S., Mitsunari K., Nakao M., 2001) This article documents a study done for four years on the functional consequences of stressing micro-arthropod. They were exposed to components of polluted rain. These components include nitric acid sulfuric acid, ammonium sulfate and other elements. The compared plots sprayed with the polluted rainwater compared to plots sprayed with distilled water. They found that the polluted waters drastically affected the abundance of five key stone species. (Heneghan L., Bolger T., 1996) Another group of scholars tested the effects of anion composition of simulated acid rain, with a pH concentration of 3.0 on saline soils. The control group was watered with a pH concentration of 5.7. Samples of soil studied, collected from Korea and Japan, showed that the soils organic matter actually decreased as well as the presence of ammonia nitrogen. The amount of nutrients changed quite a bit with the increase in the amount of simulated acid rain. (Cho JY., Nishiyama M., Matsumoto S., 2002)The Penn State University Earth and Mineral Science students explored long term effects of acid rain. In their findings, they concluded acid rain negatively affects both plant leaves and soil. By leaching onto minerals, the toxins in acid rain keep the plant from receiving its needed nutrient intake. (2002) Works Cited